Method for operating an internal combustion engine

Abstract

In an internal combustion engine, wherein a combustible fuel mix is formed in a combustion chamber of the engine by fuel and by fresh gas supplied through intake ports and combustion gases discharged through exhaust ports including intake and exhaust valves, respectively, which valves are actuated by a valve operating mechanism and a spark ignition operating mode is provided in part of the load range and an operating mode with compression ignition is provided in another part of the load range and, in the event of a change in the operating mode, the opening duration of the gas exchange valves is altered while the opening times of the exhaust valves are maintained.

Description

[0001] This is a Continuation-In-Part Application of International Application PCT / EP2004 / 010280 filed Sep. 15, 2004 and claiming the priority of German application 103 48 139.7 filed Oct. 16, 2003.BACKGROUND OF THE INVENTION [0002] The invention relates to a method for operating an internal combustion engine including cylinders with pistons delimiting combustion chambers to which fuel and fresh gas are supplied and from which combustion gases are discharged via controllable inlet and outlet valves. [0003] In a reciprocating-piston internal combustion engine, a combustion chamber, in which fuel is burnt, is delimited by a longitudinally movable piston in each cylinder. Oxygen-containing fresh gas for the combustion of fuel is supplied via intake ports of the cylinders, while the combustion exhaust gases are discharged via exhaust ports. The ports are controlled by intake valves and exhaust valves which are actuated by a valve operating mechanism to carry out the cyclic charge exchan...

AI Technical Summary

Benefits of technology

[0010] It is expedient for the opening lift of the respective gas exchange valve to be shortened simultaneously with the reduction in the opening duration, in such a manner that the speed and acceleration of the moving valve parts remain within an acceptable range and in this way the kinematics of the valve mechanism are taken into account. When controlling the gas exchange valves using a cam valve operating mechanism, it is advantageous to switch to a cam contour with a short valve lift and short opening duration when changing the operating mode to the compression ignition. The shortening of the opening duration is adapted and determined by the corresponding contouring of the control cams in such a manner that in the compression ignition mode the required quantity of combustion exhaust gases is retained and is part of the mix formatted for the following working cycle of the cylinder.

Problems solved by technology

This gives rise to a deterioration in the overall efficiency of the internal combustion engine, in particular if the internal combustion engine has a cam valve mechanism and the valve closure overlap is to be set using cam contours which are designed for operation of the engine in the spark ignition cycle.

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